Travel control method and travel control apparatus

ABSTRACT

A travel control apparatus comprises a first detector configured to detect an obstacle around a subject vehicle traveling in a first lane and a second detector configured to detect a second lane adjacent to the first lane. The apparatus sets a first range at a target position for lane change in the second lane. The first range has a size equal to or larger than a size which the subject vehicle occupies on a road surface. The apparatus detects a range in the second lane as a second range located at a side of the subject vehicle, and the obstacle is absent in the range in the second lane. The apparatus permits the subject vehicle to change lanes when the second range includes the first range. A travel control method performs correction to reduce the first range or increase the second range based on a necessity level.

TECHNICAL FIELD

The present invention relates to a travel control method and a travelcontrol apparatus for controlling travel of a subject vehicle.

BACKGROUND

Travel control apparatuses for automatically performing lane change of avehicle have been conventionally known. Such a travel control apparatusmay use a known technique of determining whether or not a space for lanechange exists in an adjacent lane to the lane in which the subjectvehicle travels and executing the lane change when the space for lanechange exists in the adjacent lane (see WO2010/082353).

In the above conventional technique, even in a travel scene in which thenecessity level of lane change is high, the subject vehicle is notpermitted to change lanes until a space for lane change is found in theadjacent lane. As a consequence, uncomfortable feeling may be given tothe driver.

SUMMARY

A problem to be solved by the present invention is to provide a travelcontrol method and a travel control apparatus that are able toappropriately determine whether lane change should be performed.

According to an aspect of the present invention, the above problem issolved by providing a travel control method executed by a travel controlapparatus. The travel control apparatus comprises a first detectorconfigured to detect an obstacle around a subject vehicle traveling in afirst lane and a second detector configured to detect a second laneadjacent to the first lane. The travel control apparatus sets a firstrange at a target position for lane change in the second lane. The firstrange has a size equal to or larger than a size which the subjectvehicle occupies on a road surface. The travel control apparatus detectsa range in the second lane as a second range. The range in the secondlane is located at a side of the subject vehicle, and the obstacle isabsent in the range in the second lane. The travel control apparatuspermits the subject vehicle to change lanes when the second rangeincludes the first range. The travel control method includes reducingthe first range or increasing the second range when a necessity level oflane change in a travel scene of the subject vehicle is a predeterminedvalue or more as compared with when the necessity level is less thepredetermined value.

According to the present invention, when the necessity level of lanechange in the travel scene of the subject vehicle is high, lane changecan be readily permitted, and a determination of whether lane changeshould be performed can be appropriately performed in accordance withthe travel scene.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating the configuration of a travelcontrol apparatus according to one or more embodiments of the presentinvention;

FIG. 2 is a view illustrating an example of a table used fordetermination of a travel scene;

FIG. 3 is a flowchart (part 1) illustrating a lane change controlprocess according to a first embodiment of the present invention;

FIG. 4 is a flowchart (part 2) illustrating the lane change controlprocess according to the first embodiment of the present invention;

FIG. 5 is a flowchart (part 3) illustrating the lane change controlprocess according to the first embodiment of the present invention;

FIGS. 6A-6C are views (part 1) for describing methods of detecting anobject range;

FIGS. 6D and 6E are views (part 2) for describing methods of detectingan object range;

FIGS. 6F and 6G are views (part 3) for describing methods of detectingan object range;

FIG. 7 is a view for describing a method of setting a target positionfor lane change;

FIGS. 8A and 8B are views for describing a method of estimating theposition of another vehicle after a predetermined time;

FIGS. 9A-9C are views for describing a method of determining whether ornot an object range becomes small;

FIG. 10 illustrates an example of a screen displayed on the display ofan announcement device;

FIGS. 11A and 11B are views for describing a method of correcting arequired range based on a necessity level of lane change;

FIGS. 12A and 12B are views for describing a method of correcting arequired range based on a situation of a next adjacent lane;

FIGS. 13A-13C are views for describing methods of correcting a requiredrange based on a travel position of an adjacent vehicle in the roadwidth direction;

FIGS. 13D-13F are views for describing methods of correcting a requiredrange based on a travel position of an adjacent vehicle in the roadwidth direction;

FIGS. 14A-14C are views for describing methods of correcting a requiredrange based on a lighting state of winkers of an adjacent vehicle;

FIGS. 14D-14F are views for describing methods of correcting a requiredrange based on a lighting state of winkers of an adjacent vehicle;

FIGS. 15A and 15B are views for describing a method of correcting anobject range based on a necessity level of lane change;

FIGS. 16A and 16B are views for describing a method of correcting anobject range based on a situation of a next adjacent lane;

FIGS. 17A-17C are views for describing methods of correcting an objectrange based on a travel position of an adjacent vehicle in the roadwidth direction;

FIGS. 17D-17F are views for describing methods of correcting an objectrange based on a travel position of an adjacent vehicle in the roadwidth direction;

FIGS. 18A-18C are views for describing methods of correcting an objectrange based on a lighting state of winkers of an adjacent vehicle;

FIGS. 18D-18F are views for describing methods of correcting an objectrange based on a lighting state of winkers of an adjacent vehicle;

FIGS. 19A and 19B are views for describing a method of determiningwhether or not lane change should be performed;

FIGS. 20A-20D are views for describing the positional relationshipbetween object lane marks and the subject vehicle in the road widthdirection; and

FIG. 21 is a flowchart illustrating a lane change control processaccording to a second embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, one or more embodiments of the present invention will bedescribed with reference to the drawings. In the embodiments, a travelcontrol apparatus equipped in a vehicle will be exemplified anddescribed.

<<First Embodiment>>

FIG. 1 is a block diagram illustrating the configuration of a travelcontrol apparatus 100 according to the present embodiment. Asillustrated in FIG. 1, the travel control apparatus 100 according to thepresent embodiment has a set of sensors 110, a subject vehicle positiondetection device 120, a map database 130, onboard equipment 140, anannouncement device 150, an input device 160, a communication device170, a drive control device 180, and a control device 190. These devicesare connected to one another via a controller area network (CAN) orother in-vehicle LAN for mutually exchanging information.

The sensors 110 detect a travel state of the subject vehicle. Examplesof the sensors 110 include a front camera that captures images ahead ofthe subject vehicle, a rear camera that captures images behind thesubject vehicle, a front radar that detects obstacles ahead of thesubject vehicle, a rear radar that detects obstacles behind the subjectvehicle, side radars that detect obstacles existing at sides of thesubject vehicle, a vehicle speed sensor that detects the vehicle speedof the subject vehicle, and an in-vehicle camera that captures images ofthe driver. The sensors 110 may be represented by one of theabove-described various sensors or may also be configured with acombination of two or more sensors. The detection results of the sensors110 are output to the control device 190.

The subject vehicle position detection device 120 is composed of a GPSunit, a gyro-sensor, a vehicle speed sensor, and other necessarycomponents. The subject vehicle position detection device 120 detectsradio waves transmitted from a plurality of communication satellitesusing the GPS unit to periodically acquire positional information of atarget vehicle (subject vehicle) and detects the current position of thetarget vehicle on the basis of the acquired positional information ofthe target vehicle, angle variation information acquired from thegyro-sensor, and the vehicle speed acquired from the vehicle speedsensor. The positional information of the target vehicle detected by thesubject vehicle position detection device 120 is output to the controldevice 190.

The map database 130 stores map information that includes positionalinformation of various facilities and specific points. Specifically, themap database 130 stores positional information of merging points,branching points, tollgates, positions at which the number of lanesdecreases, service areas (SA)/parking areas (PA), etc. together with themap information. The control device 190 can refer to the map informationstored in the map database.

The onboard equipment 140 includes various modules equipped in thevehicle and can be operated by the driver. Examples of such onboardequipment include a steering, an accelerator pedal, a brake pedal, anavigation device, an audio device, an air conditioner, a hands-freeswitch, power windows, wipers, lights, flashers, and a horn. When thedriver operates the onboard equipment 140, its information is output tothe control device 190.

The announcement device 150 may be, for example, a device such as adisplay of a navigation device, a display incorporated in a rearviewmirror, a display incorporated in a meter unit, a head-up displayprojected on a windshield, and a speaker of an audio device. Theannouncement device 150 announces announcement information, which willbe described later, to the driver under the control by the controldevice 190.

The input device 160 may be, for example, a device such as a dial switchand a touch panel disposed on a display screen that allow input by thedriver's hand operation and a microphone that allows input by thedriver's voice. In the present embodiment, the driver can operate theinput device 160 thereby to input response information in response tothe announce information which is announced by the announcement device150. For example, in the present embodiment, switches of flashers orother onboard devices can also be used as the input device 160. Morespecifically, the input device 160 may be configured such that thedriver turns on the switch of a flasher thereby to input permission oflane change in response to a query as to whether or not to automaticallyperform lane change. The response information input via the input device160 is output to the control device 190.

The communication device 170 performs communication with communicationequipment located outside the vehicle. For example, the communicationdevice 170 performs vehicle-to-vehicle communication with anothervehicle, performs road-to-vehicle communication with equipment providedat a road shoulder, or performs wireless communication with aninformation server provided outside the vehicle and can thereby acquirevarious items of information from the external equipment. Theinformation acquired by the communication device is output to thecontrol device 190.

The drive control device 180 controls travel of the subject vehicle. Forexample, when the subject vehicle follows a preceding vehicle (thisoperation is referred to as “follow-up travel control,” hereinafter),the drive control device 180 controls the operation of a drive mechanism(which includes the operation of an internal-combustion engine in thecase of an engine car and the operation of an electric motor in the caseof an electric car and further includes the torque distribution for aninternal-combustion engine and electric motor in the case of a hybridcar) and the braking operation to achieve the acceleration, decelerationand vehicle speed so that the distance between the subject vehicle andthe preceding vehicle can be maintained at a constant distance. When thesubject vehicle performs lane change such as overtaking of a precedingvehicle (this operation is referred to as “lane change control,”hereinafter), the drive control device 180 controls the operation of asteering actuator to control the operation of wheels and therebyexecutes the turning control of the subject vehicle. The drive controldevice 180 controls travel of the subject vehicle in accordance withcommands from the control device 190, which will be described later.Other well-known methods can also be used as a travel control method bythe drive control device 180.

The control device 190 is composed of a read only memory (ROM) thatstores programs for controlling travel of the subject vehicle, a centralprocessing unit (CPU) that executes the programs stored in the ROM, anda random access memory (RAM) that serves as an accessible storagedevice. As substitute for or in addition to the CPU, a micro processingunit (MPU), digital signal processor (DSP), application specificintegrated circuit (ASIC), field programmable gate array (FPGA), or thelike can also be used.

The control device 190 executes the programs stored in the ROM using theCPU thereby to achieve a travel information acquisition function toacquire information regarding a travel state of the subject vehicle, atravel scene determination function to determine a travel scene of thesubject vehicle, a travel control function to control travel of thesubject vehicle, and a lane change control function to control lanechange through a determination as to whether or not lane change shouldbe performed. Each function of the control device 190 will be describedbelow.

The control device 190 uses the travel information acquisition functionto acquire the travel information regarding the travel state of thesubject vehicle. For example, the control device 190 can use the travelinformation acquisition function to acquire the external imageinformation around the vehicle captured by the front camera and rearcamera and/or the detection results by the front radar, rear radar, andside radars as the travel information. The control device 190 can alsouse the travel information acquisition function to acquire the vehiclespeed information of the subject vehicle detected by the vehicle speedsensor and/or the image information of the driver's face captured by thein-vehicle camera as the travel information.

The control device 190 can use the travel information acquisitionfunction further to acquire information on the current position of thesubject vehicle from the subject vehicle position detection device 120as the travel information and also to acquire positional information ofmerging points, branching points, tollgates, positions at which thenumber of lanes decreases, service areas (SA)/parking areas (PA), etc.from the map database 130 as the travel information. In addition, thecontrol device 190 can use the travel information acquisition functionto acquire information on the operation of the onboard equipment 140 bythe driver from the onboard equipment 140 as the travel information.

The control device 190 uses the travel scene determination function torefer to a table stored in the ROM of the control device 190 todetermine the travel scene in which the subject vehicle is traveling.FIG. 2 is a view illustrating an example of the table used to determinethe travel scene. As illustrated in FIG. 2, the table stores a travelscene suitable for lane change and its determination condition for eachtravel scene. The control device 190 uses the travel scene determinationfunction to refer to the table illustrated in FIG. 2 to determinewhether or not the travel scene of the subject vehicle is a travel scenesuitable for lane change.

For example, in the example illustrated in FIG. 2, the determinationcondition for a “scene of catching up with a preceding vehicle” isdefined by four conditions: a condition of “detecting a precedingvehicle ahead,” a condition of “the vehicle speed of the precedingvehicle<the vehicle speed of the subject vehicle,” a condition of“reaching the preceding vehicle within a predetermined time,” and acondition that “the direction of lane change is not under a lane changeprohibition condition.” The control device 190 uses the travel scenedetermination function to determine whether or not the subject vehiclesatisfies the above conditions, for example, on the basis of thedetection results by the front camera and/or front radar, the vehiclespeed of the subject vehicle detected by the vehicle speed sensor, thepositional information of the subject vehicle, etc. When the aboveconditions are satisfied, the travel scene determination function isused to determine that the subject vehicle is in the “scene of catchingup with a preceding vehicle.” Similarly, for all other travel scenesregistered in the scene determination table, the travel scenedetermination function is used to determine whether or not eachdetermination condition is satisfied.

Examples of the lane change prohibition condition include a conditionthat “the subject vehicle is traveling in a lane change prohibitionarea,” a condition that “an obstacle exists in the direction of lanechange,” a condition that “the subject vehicle will get across acenterline (road center line),” and a condition that “the subjectvehicle will enter a road shoulder or get across a road end.” On a roadon which emergency stop is permitted at a road shoulder or the like inan “emergency evacuation scene,” the condition that “the subject vehiclewill enter a road shoulder or get across a road end” may be permitted inthe “emergency evacuation scene.” In the table illustrated in FIG. 2,the necessity level of lane change, the time limit, and the direction oflane change will be described later.

When the travel scene of the subject vehicle corresponds to a pluralityof travel scenes, the control device 190 can use the travel scenedetermination function to determine a travel scene having a highernecessity level of lane change as the travel scene of the subjectvehicle. For example, it is assumed that, in the example illustrated inFIG. 2, the travel scene of the subject vehicle corresponds to a “sceneof catching up with a preceding vehicle” and a “scene of lane transfertoward a destination.” It is also assumed in this case that thenecessity level X1 of lane change in the “scene of catching up with apreceding vehicle” is lower than the necessity level X8 of lane changein the “scene of lane transfer toward a destination” (X1<X8). In thiscase, the control device 190 can use the travel scene determinationfunction to determine the “scene of lane transfer toward a destination”with the higher necessity level of lane change as the travel scene ofthe subject vehicle.

The control device 190 uses the travel control function to controltravel of the subject vehicle. For example, the control device 190 usesthe travel control function to detect lane marks of a lane in which thesubject vehicle travels (also referred to as a “subject vehicle lane,”hereinafter) on the basis of the detection results of the sensors 110and perform lane keeping control to control a travel position of thesubject vehicle in the road width direction. In this case, the controldevice 190 can use the travel control function to allow the drivecontrol device 180 to control the operation of the steering actuator andthe like so that the subject vehicle travels at an appropriate travelposition. In addition or alternatively, the control device 190 can usethe travel control function to perform the follow-up travel control toautomatically follow a preceding vehicle with a certain distance fromthe preceding vehicle. In this case, the control device 190 can use thetravel control function to allow the drive control device 180 to controlthe operation of the drive mechanism such as an engine and brake so thatthe subject vehicle travels with a constant distance between the subjectvehicle and the preceding vehicle. In the following description, theautomatic travel control will be described as including the lane keepingcontrol and the follow-up travel control.

The control device 190 uses the lane change control function todetermine whether or not to perform lane change on the basis of thetravel scene of the subject vehicle and/or information on obstaclesexisting around the subject vehicle. When a determination is made toperform lane change, the control device 190 can use the lane changecontrol function to allow the drive control device 180 to control theoperation of the steering actuator. Details of a method of controllinglane change using the lane change control function will be describedlater.

A lane change control process according to the first embodiment will nowbe described with reference to FIG. 3 to FIG. 5. FIG. 3 to FIG. 5 areflowcharts illustrating the lane change control process according to thefirst embodiment. As will be understood, the lane change control processdescribed below is executed by the control device 190. The descriptionwill be made below on the assumption that the control device 190 usesthe travel control function to perform the follow-up travel control forthe subject vehicle to follow a preceding vehicle.

First, in step S101, the control device 190 uses the travel informationacquisition function to acquire the travel information regarding thetravel state of the subject vehicle. In step S102, the control device190 uses the travel scene determination function to determine the travelscene of the subject vehicle on the basis of the travel informationacquired in step S101.

In step S103, the control device 190 uses the travel scene determinationfunction to determine whether or not the travel scene of the subjectvehicle determined in step S102 is a travel scene suitable for lanechange. Specifically, when the travel scene of the subject vehicle isany of travel scenes illustrated in FIG. 2, the travel scenedetermination function is used to determine that the travel scene of thesubject vehicle is a travel scene suitable for lane change. When thetravel scene of the subject vehicle is not a travel scene suitable forlane change, the routine returns to step S101 from which thedetermination of the travel scene is repeated. When the travel scene ofthe subject vehicle is a travel scene suitable for lane change, theroutine proceeds to step S104.

In step S104, the control device 190 uses the lane change controlfunction to detect an object range. In the present embodiment, thecontrol device 190 uses the lane change control function to detectobstacles existing around the subject vehicle on the basis of theexternal image information around the vehicle captured by the frontcamera and rear camera and/or the travel information including thedetection results by the front radar, rear radar, and side radars. Thecontrol device 190 uses the lane change control function to detect arange that is located at a side of the subject vehicle and in which noobstacles exist, as the object range. The object range refers to arelative range with reference to the travel position when the subjectvehicle travels at the current speed. When another vehicle existingaround the subject vehicle travels straight ahead at the same speed asthe subject vehicle, therefore, the object range does not vary. The“side of the subject vehicle” refers to a range in which the position atthe side of the subject vehicle can be taken as a target position forlane change when the subject vehicle changes lanes (this target positionis also a relative position with reference to the travel position whenthe subject vehicle travels at the current speed), and this range (suchas direction, size, and angle) can be appropriately set. Methods ofdetecting an object range will be described below with reference toFIGS. 6A-6G. FIGS. 6A-6G are views for describing object ranges.

In the exemplary scene illustrated in FIG. 6A, no other vehicles asobstacles exist in an adjacent lane to the subject vehicle lane. Thecontrol device 190 can therefore use the lane change control function todetect the adjacent lane as an object range. As will be understood, roadshoulders are excluded from the object range because the road shouldersare basically within ranges in which lane change cannot be performed.However, when the travel scene of the subject vehicle is an “emergencyevacuation scene” on a road on which emergency stop or the like ispermitted at a road shoulder, the road shoulder can be included in theobject range (here and hereinafter).

In the exemplary scene illustrated in FIG. 6B, other vehicles asobstacles exist in an adjacent lane to the subject vehicle lane.However, there is a range in which no other vehicles exist between theother vehicle located ahead of the subject vehicle and the other vehiclelocated behind the subject vehicle. The control device 190 can thereforeuse the lane change control function to detect that range as an objectrange. In the exemplary scene illustrated in FIG. 6C, the adjacent laneincludes a range in which no other vehicles exist, as in the sceneillustrated in FIG. 6B, and also in the next lane adjacent to theadjacent lane (also referred to as a “next adjacent lane,” hereinafter),there is a range in which no other vehicles exist between the othervehicle located ahead and the other vehicle located behind. In thiscase, the control device 190 can use the lane change control function todetect the range in which no other vehicles exist in the adjacent laneand the range in which no other vehicles exist in the next adjacent laneas object ranges.

In addition or alternatively, the control device 190 may use the lanechange control function to detect an object range by excluding a range,such as a construction section as illustrated in FIG. 6D, in which thesubject vehicle cannot travel, from the object range. Examples of such arange in which the subject vehicle cannot travel include a range inwhich another vehicle parks or stops and a range in which vehicles areprohibited from traveling due to traffic regulation, etc., in additionto a construction section. When, as illustrated in FIG. 6D, the range inwhich the subject vehicle cannot travel due to a construction section orthe like occupies half or more of the adjacent lane (half or more in theroad width direction), for example, the remaining less than half of therange may not be detected as an object range.

When, as illustrated in FIG. 6E, other vehicles are traveling in seriesin the adjacent lane and no space for lane change exists in the adjacentlane, the control device 190 can use the lane change control function todetermine that an object range cannot be detected.

The exemplary scene illustrated in FIG. 6F is a scene in which thesubject vehicle is traveling on a road on which lane change from theadjacent lane to the next adjacent lane is prohibited. On such a road,the control device 190 uses the lane change control function to detect arange in which no obstacles exist in the adjacent lane to which lanechange is possible, as an object range. That is, in this case, the nextadjacent lane to which lane change cannot be performed is not detectedas an object range. The exemplary scene illustrated in FIG. 6G is ascene in which the subject vehicle is traveling on a road havingoncoming lanes. On such a road, the control device 190 uses the lanechange control function to detect an object range only in a lane in thesame direction as the travel direction of the subject vehicle. That is,in this case, an object range is not detected in the oncoming lanes.

In the present embodiment, the control device 190 uses the lane changecontrol function to detect an object range in a direction, among rightand left directions, which is suitable for lane change in the travelscene of the subject vehicle. In the present embodiment, the directionsuitable for lane change in each travel scene is preliminarily stored inthe table illustrated in FIG. 2. The control device 190 uses the lanechange control function to refer to the table illustrated in FIG. 2 toacquire information on the “direction of lane change” in the travelscene of the subject vehicle. For example, when the travel scene of thesubject vehicle is a “scene of catching up with a preceding vehicle,”the control device 190 uses the lane change control function to refer tothe table of FIG. 2 to acquire a “direction toward the overtaking laneside” as the “direction of lane change.” Then, the control device 190uses the lane change control function to detect an object range in the“direction of lane change.” For example, when the travel scene of thesubject vehicle is a “scene of catching up with a preceding vehicle,”the control device 190 uses the lane change control function to detectan object range in the “direction toward the overtaking lane side,” thatis, in the direction toward a lane in which travel of an overtakingvehicle is recommended (e.g. the rightward direction in the examplesillustrated in FIG. 6A to FIG. 6D. Thus, the lane change controlfunction can be used to detect an object range in the direction of lanechange suitable for the travel scene of the subject vehicle.

In addition or alternatively, the control device 190 may use the lanechange control function to detect an object range at a side of thesubject vehicle. For example, even when a range is detected in which noobstacles exist in the adjacent lane, if the range is separate from thecurrent position of the subject vehicle by a certain distance or moreand located behind or ahead of the subject vehicle, it may be difficultto perform lane change to such a range, which is therefore not detectedas an object range.

In step S105, the control device 190 uses the lane change controlfunction to set a target position for lane change. For example, asillustrated in FIG. 7, the control device 190 can use the lane changecontrol function to set a position that is within the object range inthe adjacent lane detected in step S104 and that is shifted backwardfrom the position of the subject vehicle by a small distance, as thetarget position for lane change (e.g. position of the vehicle indicatedby the dashed line in FIG. 7). The target position for lane change is arelative position with respect to the position at which the subjectvehicle travels. That is, provided that the position when the subjectvehicle travels at the current speed without changing the speed is areference position, a position located laterally behind the referenceposition by a small distance can be set as the target position for lanechange. This allows the subject vehicle to change lanes to the adjacentlane without accelerating the subject vehicle when the subject vehiclemoves to the target position for lane change. FIG. 7 is a view fordescribing a method of setting the target position for lane change.

The control device 190 can use the lane change control function to setthe target position for lane change by taking into account the ease oflane change, such as a situation that the object range in the adjacentlane includes a range to which the subject vehicle can move and asituation that another vehicle that may enter the object range does notexist around the subject vehicle. For example, when another vehicleexisting around the object range lights the winkers toward the objectrange and/or travels while deviating toward the object range side, thelane change control function can be used to determine that the othervehicle may enter the object range. In this case, another position in anobject range which the other vehicle is less likely to enter can be setas the target position. In the above exemplary case, the target positionfor lane change is set at a position located behind the subject vehiclewithin the object range in the adjacent lane. In an alternativeembodiment, the target position for lane change may be set at a positionlocated ahead of the subject vehicle within the object range in theadjacent lane. In an alternative embodiment, step S105 may includesetting a target route for changing lanes instead of setting the targetposition for lane change.

In step S106, the control device 190 uses the lane change controlfunction to estimate a required time Ti for lane change. For example,the control device 190 can use the lane change control function toestimate a time required for the subject vehicle to move from thecurrent position to the target position for lane change as the requiredtime T1 on the basis of the vehicle speed and/or acceleration of thesubject vehicle.

In step S107, the control device 190 uses the lane change controlfunction to estimate an object range after the predetermined time T1estimated in step S106. Specifically, the control device 190 uses thelane change control function to estimate the travel position after thepredetermined time T1 of another vehicle existing around the subjectvehicle on the basis of the vehicle speed and acceleration of the othervehicle. For example, the control device 190 uses the lane changecontrol function to repeatedly detect the positional information of theother vehicle thereby to measure the speed vector v0, accelerationvector a0, and positional vector p0 of the other vehicle, as illustratedin FIG. 8A.

As illustrated in FIG. 8A, when the travel direction of the subjectvehicle is along X-axis and the road width direction is along Y-axis,the speed vector v0 of the other vehicle is represented by the followingequation (1):v0=vx0i+vy0j  (1)where vx0 represents a speed component in the X-axis direction of thespeed vector of the other vehicle and vy0 represents a speed componentin the Y-axis direction of the speed vector of the other vehicle. In theabove equation (1), i represents a unit vector in the X-axis directionand j represents a unit vector in the Y-axis direction (the same appliesto the following equations (2), (3), and (6)).

The acceleration vector a0 of the other vehicle can be obtained asrepresented by the following equation (2) while the positional vector p0of the other vehicle can be obtained as represented by the followingequation (3).a0=ax0i+ay0j  (2)p0=px0i+py0j  (3)In the above equation (2), ax0 represents an acceleration component inthe X-axis direction of the acceleration vector of the other vehicle anday0 represents an acceleration component in the Y-axis direction of theacceleration vector of the other vehicle. In the above equation (3), px0represents a positional component in the X-axis direction of thepositional vector of the other vehicle and py0 represents a positionalcomponent in the Y-axis direction of the positional vector of the othervehicle.

Then, the control device 190 uses the lane change control function tocalculate a positional vector pT1 after the predetermined time T1 of theother vehicle, as illustrated in FIG. 8B. Specifically, the controldevice 190 uses the lane change control function to calculate thepositional vector pT1 after the predetermined time T1 of the othervehicle on the basis of the following equations (4) to (6).pxT1=px0+vx0T1+1/2(ax0T1)²  (4)pyT1=py0+vy0T1+1/2(ay0T1)²  (5)pT1=pxT1i+pyT1j  (6)In the above equations (4) and (5), pxT1 represents a positionalcomponent in the X-axis direction of the positional vector pT1 after thepredetermined time T1 of the other vehicle, pyT1 represents a positionalcomponent in the Y-axis direction of the positional vector pT1 after thepredetermined time T1 of the other vehicle, vx0T1 represents a movingspeed in the X-axis direction of the other vehicle after thepredetermined time T1, vy0T1 represents a moving speed in the Y-axisdirection of the other vehicle after the predetermined time T 1, ax0T1represents acceleration in the X-axis direction of the other vehicleafter the predetermined time T1, and ay0T1 represents acceleration inthe Y-axis direction of the other vehicle after the predetermined timeT1.

The control device 190 uses the lane change control function to estimatepositions after the predetermined time T1 of all other vehicles existingaround the subject vehicle. Then, the control device 190 uses the lanechange control function to estimate an object range after thepredetermined time T1 on the basis of the positions after thepredetermined time T1 of the other vehicles. The control device 190 canuse the lane change control function to estimate the object range afterthe predetermined time T1 by taking into account the situation of laneregulation after the predetermined time T1, existence of obstacles onthe road, presence or absence of obstruction in the adjacent lane, andexistence of a section, such as a construction section, to which thesubject vehicle cannot move. The control device 190 can use the lanechange control function to estimate an object range after thepredetermined time T1 as in step S104.

In step S108, the control device 190 uses the lane change controlfunction to estimate whether or not the object range becomes small inthe adjacent lane after the predetermined time T1 on the basis of thecurrent object range detected in step S104 and the object range afterthe predetermined time T1 estimated in step S107. FIGS. 9A-9C are viewsfor describing a method of determining whether or not the object rangebecomes small.

In the example illustrated in FIGS. 9A-9C, it is assumed, for example,that the current object range is an object range illustrated in FIG. 9Awhile the object range after the predetermined time T1 is an objectrange illustrated in FIG. 9B. In this case, the control device 190 usesthe lane change control function to compare the current object range ofFIG. 9A and the object range after the predetermined time T1 of FIG. 9Bto determine whether or not the object range in the adjacent lanebecomes small after the predetermined time T1. Specifically, the controldevice 190 uses the lane change control function to overlap the currentobject range of FIG. 9A and the object range after the predeterminedtime T1 of FIG. 9B and estimate that the object range becomes small inthe adjacent lane when the size of the current object range in theadjacent lane is larger than the size of the object range after thepredetermined time T1 in the adjacent lane. Then, when it is estimatedthat the object range in the adjacent lane becomes small after thepredetermined time T1, the routine proceeds to step S109 in whichannouncement information is announced that the object range will becomesmall after the predetermined time T1. For example, the control device190 can use the lane change control function to announce an alarm thatthe object range will become small after the predetermined time T1,using the display and/or speaker of the announcement device 150.

In step S108, the control device 190 also uses the lane change controlfunction to compare the current object range of FIG. 9A and the objectrange after the predetermined time T1 of FIG. 9B to specifydisappearance ranges. The disappearance ranges refer to ranges that willdisappear from the object range after the predetermined time T1 asillustrated in FIG. 9C, that is, ranges that are included in the currentobject range of FIG. 9A but will not be included in the object rangeafter the predetermined time T1 of FIG. 9B. In addition, the controldevice 190 uses the lane change control function to compare the currentobject range of FIG. 9A and the object range after the predeterminedtime T1 of FIG. 9B to specify an additional range. The additional rangerefers to a range that will be added to the object range after thepredetermined time T1 as illustrated in FIG. 9C, that is, a range thatis not included in the current object range of FIG. 9A but will beincluded in the object range after the predetermined time T1 of FIG. 9B.

Then, when a disappearance range or an additional range is specified,the control device 190 can use the lane change control function in stepS109 to announce the announcement information, which includesinformation on the disappearance range or additional range, to thedriver. For example, in the scene illustrated in FIG. 9C, the controldevice 190 can use the lane change control function to display thedisappearance ranges and the additional range on the display of theannouncement device 150 in different display forms, as illustrated inFIG. 10. This allows the driver to appropriately perceive thedisappearance ranges and the additional range. FIG. 10 is a viewillustrating an example of the announcement information displayed on thedisplay of the announcement device 150.

The control device 190 can use the lane change control function toannounce the announcement information that the object range will becomesmall only when the size of the object range is to become small afterthe predetermined time T1 to a predetermined range or more. In additionor alternatively, the control device 190 can use the lane change controlfunction to announce the disappearance range and/or the additional rangewhen the size of the disappearance range and/or additional range is notsmaller than a predetermined size. In addition or alternatively, thecontrol device 190 can use the lane change control function to changethe display form of the disappearance range or the display form of theobject range after the predetermined time T1 in accordance with the sizeof the disappearance range. For example, the control device 190 can usethe lane change control function to change the display form of thedisappearance range or the display form of the object range after thepredetermined time T1 between a case in which the size of thedisappearance range is a predetermined range or more and a case in whichthe size of the disappearance range is less than the predeterminedrange. In an example, the control device 190 can use the lane changecontrol function to display the disappearance range or the object rangeafter the predetermined time T1 in green color or the like when the sizeof the disappearance range is less than a predetermined range anddisplay the disappearance range or the object range after thepredetermined time T1 in red color or the like in an emphasized mannerwhen the size of the disappearance range is the predetermined range ormore. In addition or alternatively, the control device 190 can use thelane change control function to display the disappearance range or theobject range after the predetermined time T1 in a blinking manner whenthe size of the disappearance range is a predetermined range or more. Inaddition or alternatively, when the size of the disappearance range is apredetermined range or more, an alarm lamp provided in an indicator maybe configured to light. In addition or alternatively, provided that theannouncement device 150 includes a speaker, the speaker may beconfigured to output sound of a tone and/or volume level that getattention of the driver when the size of the disappearance range is apredetermined range or more, as compared with when the size of thedisappearance range is less than the predetermined range. In addition oralternatively, the control device 190 can use the lane change controlfunction to change the display form of the disappearance range inaccordance with the rate with which the object range becomes small. Forexample, when the rate with which the object range becomes small is apredetermined rate or more, the control device 190 can use the lanechange control function to display the disappearance range or the objectrange after the predetermined time T1 in an emphasized manner, such asin red color and in a blinking manner.

In step S110, the control device 190 uses the lane change controlfunction to acquire information on a required range. The required rangerefers to a range having a size necessary for the subject vehicle tochange lanes, or a range having a size that is at least equal to orlarger than a size which the subject vehicle occupies on a road surface.Although details will be described later, in the present embodiment,when a required range is set at the target position for lane change andthe object range in the adjacent lane includes the required range, adetermination is made that a space corresponding to the required rangeexists within the object range in the adjacent lane, and lane change ispermitted. In the present embodiment, the memory of the control device190 stores information including the shape and size of the requiredrange, and the lane change control function can be used to acquire theinformation on the required range from the memory of the control device190.

In step S111, the control device 190 uses the lane change controlfunction to correct the required range acquired in step S110. The lanechange control function can be used to correct the required range on thebasis of any one of conditions described below or on the basis of acombination of two or more of these conditions.

First, the control device 190 can use the lane change control functionto correct the required range in accordance with a necessity level oflane change in the travel scene of the subject vehicle. In the presentembodiment, the table illustrated in FIG. 2 preliminarily stores thenecessity level of lane change in each travel scene. The control device190 uses the lane change control function to refer to the tableillustrated in FIG. 2 to acquire the necessity level of lane change inthe travel scene of the subject vehicle. For example, in the “scene ofcatching up with a preceding vehicle,” the control device 190 can usethe lane change control function to refer to the table illustrated inFIG. 2 to acquire “X1” as the necessity level of lane change. Then, whenthe necessity level X1 of lane change is high (when the necessity levelof lane change is a predetermined value or higher), the control device190 can use the lane change control function to reduce the length of therequired range in the travel direction of the subject vehicle ascompared with the case of a low necessity level of lane change(the casein which the necessity level of lane change is less than thepredetermined value), thereby reducing the required range in the traveldirection of the subject vehicle. For example, in the exampleillustrated in FIGS. 11A and 11B, provided that FIG. 11A represents therequired range before correction, when the necessity level X1 of lanechange is high (when the necessity level of lane change is apredetermined value st1 or higher), the control device 190 can use thelane change control function to reduce the required range in the traveldirection of the subject vehicle as illustrated in FIG. 11B. As will beunderstood, the control device 190 uses the lane change control functionto correct the required range within a range that is not smaller thanthe range which the subject vehicle occupies the road surface. Inaddition or alternatively, the control device 190 can use the lanechange control function to reduce the required range as the necessitylevel of lane change in the travel scene of the subject vehicleincreases. In addition or alternatively, although not illustrated, whenthe necessity level X1 of lane change is low (when the necessity levelof lane change is lower than a predetermined value st2 (st1>st2)), thecontrol device 190 can use the lane change control function to increasethe required range in the travel direction of the subject vehicle ascompared with the required range before correction.

Second, the control device 190 can use the lane change control functionto detect an object range with no other vehicles in the next laneadjacent to the adjacent lane (next adjacent lane) and correct therequired range on the basis of the detected object range in the nextadjacent lane. For example, when a space (e.g. a space corresponding tothe required range) to which another vehicle traveling in the adjacentlane (also referred to as an “adjacent vehicle,” hereinafter) can changelanes is detected in the object range in the next adjacent lane, thatis, when a space to which the adjacent vehicle can change lanes can bedetected in the next adjacent lane, the control device 190 can use thelane change control function to reduce the required range. Specifically,when a space to which the adjacent vehicle can change lanes can bedetected in the next adjacent lane, the control device 190 uses the lanechange control function to reduce the length of the required range inthe travel direction of the subject vehicle, thereby reducing therequired range in the travel direction of the subject vehicle. Forexample, in the example illustrated in FIGS. 12A and 12B, provided thatFIG. 12A represents the required range before correction, when a spaceto which the adjacent vehicle can change lanes can be detected in thenext adjacent lane, the control device 190 can use the lane changecontrol function to reduce the length of the required range in thetravel direction of the subject vehicle as illustrated in FIG. 12B,thereby reducing the required range in the travel direction of thesubject vehicle. In addition or alternatively, the control device 190can use the lane change control function to reduce the required range inthe travel direction of the subject vehicle as the space to which theadjacent vehicle can change lanes increases in the next adjacent lane.

Third, the control device 190 can use the lane change control functionto correct the required range on the basis of the travel position in theroad width direction of another vehicle traveling in the adjacent lane(adjacent vehicle). Specifically, the control device 190 uses the lanechange control function to detect the travel position of the adjacentvehicle in the road width direction. When the travel position of theadjacent vehicle in the road width direction is nearer to the subjectvehicle lane side than the center of the adjacent lane, the controldevice 190 uses the lane change control function to increase the lengthof the required range in the travel direction of the subject vehiclethereby to increase the required range. More specifically, the controldevice 190 uses the lane change control function to increase the lengthof the required range in the frontward direction with respect to thesubject vehicle when the adjacent vehicle travels ahead of the subjectvehicle and increase the length of the required range in the rearwarddirection with respect to the subject vehicle when the adjacent vehicletravels behind the subject vehicle. For example, in the exampleillustrated in FIGS. 13A-13C, provided that FIG. 13A represents therequired range before correction, the control device 190 can use thelane change control function to increase the required range frontwardwhen the adjacent vehicle travels ahead of the subject vehicle andnearer to the subject vehicle lane side than the center of the adjacentlane as illustrated in FIG. 13B and increase the required range rearwardwhen the adjacent vehicle travels behind the subject vehicle and nearerto the subject vehicle lane side than the center of the adjacent lane asillustrated in FIG. 13C. In addition or alternatively, the controldevice 190 can use the lane change control function to increase therequired range in the travel direction of the subject vehicle as theadjacent vehicle is nearer to the subject vehicle lane side (as thedistance in the road width direction from lane marks at the subjectvehicle lane side of the adjacent lane to the adjacent vehicle isshorter).

In addition or alternatively, when the travel position of the adjacentvehicle in the road width direction is nearer to the opposite side tothe subject vehicle lane than the center of the adjacent lane, thecontrol device 190 uses the lane change control function to reduce thelength of the required range in the travel direction of the subjectvehicle thereby to reduce the required range. More specifically, thecontrol device 190 uses the lane change control function to reduce therequired range from ahead when the adjacent vehicle travels ahead of thesubject vehicle and reduce the required range from behind when theadjacent vehicle travels behind the subject vehicle. For example, in theexample illustrated in FIGS. 13D-13F, provided that FIG. 13D representsthe required range before correction, the control device 190 can use thelane change control function to reduce the required range from aheadwhen the adjacent vehicle travels ahead of the subject vehicle andnearer to the opposite side to the subject vehicle lane than the centerof the adjacent lane as illustrated in FIG. 13E and reduce the requiredrange from behind when the adjacent vehicle travels behind the subjectvehicle and nearer to the opposite side to the subject vehicle lane thanthe center of the adjacent lane as illustrated in FIG. 13F. In additionor alternatively, the control device 190 can use the lane change controlfunction to reduce the required range in the travel direction of thesubject vehicle as the adjacent vehicle is nearer to the opposite sideto the subject vehicle lane (as the distance in the road width directionfrom lane marks at the subject vehicle lane side of the adjacent lane tothe adjacent vehicle is longer).

Fourth, the control device 190 can use the lane change control functionto correct the required range on the basis of a lighting state ofwinkers of another vehicle traveling in the adjacent lane (adjacentvehicle). Specifically, the control device 190 uses the lane changecontrol function to detect the lighting state of winkers of the adjacentvehicle. When the adjacent vehicle lights the winkers at the subjectvehicle lane side, the control device 190 uses the lane change controlfunction to increase the length of the required range in the traveldirection of the subject vehicle thereby to increase the required range.More specifically, the control device 190 uses the lane change controlfunction to increase the length of the required range in the frontwarddirection with respect to the subject vehicle when the adjacent vehicletraveling ahead of the subject vehicle lights the winkers at the subjectvehicle lane side and increase the length of the required range in therearward direction with respect to the subject vehicle when the adjacentvehicle traveling behind the subject vehicle lights the winkers at thesubject vehicle lane side. For example, in the example illustrated inFIGS. 14A-14C, provided that FIG. 14A represents the required rangebefore correction, the control device 190 can use the lane changecontrol function to increase the required range frontward when theadjacent vehicle travels ahead of the subject vehicle while lighting thewinkers at the subject vehicle lane side. When the adjacent vehicletravels behind the subject vehicle while lighting the winkers at thesubject vehicle lane side as illustrated in FIG. 14C, the control device190 can use the lane change control function to increase the requiredrange rearward.

In addition or alternatively, when the adjacent vehicle lights thewinkers at the opposite side to the subject vehicle lane, the controldevice 190 uses the lane change control function to reduce the length ofthe required range in the travel direction of the subject vehiclethereby to reduce the required range. More specifically, the controldevice 190 uses the lane change control function to reduce the requiredrange from ahead when the adjacent vehicle traveling ahead of thesubject vehicle lights the winkers at the opposite side to the subjectvehicle lane and reduce the required range from behind when the adjacentvehicle traveling behind the subject vehicle lights the winkers at theopposite side to the subject vehicle lane. For example, in the exampleillustrated in FIGS. 14D-F, provided that FIG. 14D represents therequired range before correction, the control device 190 can use thelane change control function to reduce the required range from aheadwhen the adjacent vehicle travels ahead of the subject vehicle whilelighting the winkers at the opposite side to the subject vehicle lane.When the adjacent vehicle travels behind the subject vehicle whilelighting the winkers at the opposite side to the subject vehicle lane asillustrated in FIG. 14F, the control device 190 can use the lane changecontrol function to reduce the required range from behind.

Fifth, the control device 190 can use the lane change control functionto correct the required range on the basis of the speed and/oracceleration of another vehicle traveling in the adjacent lane (adjacentvehicle). Specifically, the control device 190 uses the lane changecontrol function to detect the speed and acceleration of the adjacentvehicle and estimate whether or not the adjacent vehicle comes away fromthe subject vehicle from the speed and acceleration of the adjacentvehicle, for example, as illustrated in FIGS. 8A and 8B. Then, when theadjacent vehicle is estimated to come away from the subject vehicle, thecontrol device 190 uses the lane change control function to reduce thelength of the required range in the travel direction of the subjectvehicle thereby to reduce the required range in the travel direction ofthe subject vehicle. More specifically, the control device 190 uses thelane change control function to reduce the required range from aheadwhen the adjacent vehicle traveling ahead of the subject vehicle comesaway from the subject vehicle and reduce the required range from behindwhen the adjacent vehicle traveling behind the subject vehicle comesaway from the subject vehicle.

In addition or alternatively, when the adjacent vehicle is estimated tocome close to the subject vehicle, the control device 190 uses the lanechange control function to increase the length of the required range inthe travel direction of the subject vehicle thereby to increase therequired range in the travel direction of the subject vehicle. Morespecifically, the control device 190 uses the lane change controlfunction to increase the required range frontward when the adjacentvehicle traveling ahead of the subject vehicle comes close to thesubject vehicle and increase the required range rearward when theadjacent vehicle traveling behind the subject vehicle comes close to thesubject vehicle.

In an alternative embodiment, step S111 may include correcting theobject range in the adjacent lane instead of correcting the requiredrange.

For example, the control device 190 can use the lane change controlfunction to correct the object range in the adjacent lane in accordancewith the necessity level of lane change in the travel scene of thesubject vehicle as illustrated in FIGS. 15A and 15B instead of using thelane change control function to correct the required range in accordancewith the necessity level of lane change in the travel scene of thesubject vehicle as illustrated in FIGS. 11A and 11B. Specifically, whenthe necessity level of lane change is high (when the necessity level oflane change is a predetermined value or higher), the control device 190can use the lane change control function to increase the length of theobject range in the adjacent lane in the travel direction of the subjectvehicle as compared with the case of a low necessity level of lanechange (the case in which the necessity level of lane change is lessthan the predetermined value), thereby reducing the object range in theadjacent lane in the travel direction of the subject vehicle. Forexample, in the example illustrated in FIGS. 15A and 15B, provided thatFIG. 15A represents the object range in the adjacent lane beforecorrection, when the necessity level of lane change is high (when thenecessity level of lane change is a predetermined value or higher), thecontrol device 190 can use the lane change control function to increasethe object range in the adjacent lane in the travel direction of thesubject vehicle as illustrated in FIG. 15B. In addition oralternatively, the control device 190 can use the lane change controlfunction to increase the object range in the adjacent lane as thenecessity level of lane change in the travel scene of the subjectvehicle increases.

The control device 190 can use the lane change control function tocorrect the object range in the adjacent lane on the basis of the objectrange in the next adjacent lane as illustrated in FIGS. 16A and 16Binstead of using the lane change control function to correct therequired range on the basis of the object range in the next adjacentlane as illustrated in FIGS. 12A and 12B. For example, in the exampleillustrated in FIGS. 16A and 16B, provided that FIG. 16A represents theobject range in the adjacent lane before correction, when a space (e.g.a space corresponding to the required range) to which the adjacentvehicle can change lanes can be detected in the object range in the nextadjacent lane, the control device 190 can use the lane change controlfunction to increase the length of the object range in the adjacent lanein the travel direction of the subject vehicle as illustrated in FIG.16B, thereby increasing the object range in the adjacent lane in thetravel direction of the subject vehicle. In addition or alternatively,the control device 190 can use the lane change control function toincrease the object range in the adjacent lane in the travel directionof the subject vehicle as the object range in the next adjacent laneincreases.

The control device 190 can use the lane change control function tocorrect the object range on the basis of the travel position in the roadwidth direction of another vehicle traveling in the adjacent lane(adjacent vehicle) as illustrated in FIGS. 17A-17F instead of using thelane change control function to correct the required range on the basisof the travel position of the adjacent vehicle in the road widthdirection as illustrated in FIGS. 13A-13F. Specifically, the controldevice 190 uses the lane change control function to detect the travelposition of the adjacent vehicle in the road width direction. When thetravel position of the adjacent vehicle in the road width direction isnearer to the subject vehicle lane side than the center of the adjacentlane, the control device 190 uses the lane change control function toreduce the object range in the adjacent lane in the travel direction ofthe subject vehicle. More specifically, the control device 190 uses thelane change control function to reduce the object range in the adjacentlane from ahead of the subject vehicle when the adjacent vehicle travelsahead of the subject vehicle and reduce the object range in the adjacentlane from behind the subject vehicle when the adjacent vehicle travelsbehind the subject vehicle. For example, in the example illustrated inFIGS. 17A-17C, provided that FIG. 17A represents the object range in theadjacent lane before correction, the control device 190 can use the lanechange control function to reduce the object range in the adjacent lanefrom ahead when the adjacent vehicle travels ahead of the subjectvehicle and nearer to the subject vehicle lane side as illustrated inFIG. 17B. When the adjacent vehicle travels behind the subject vehicleand nearer to the subject vehicle lane side as illustrated in FIG. 17C,the control device 190 can use the lane change control function toreduce the object range in the adjacent lane from behind. In addition oralternatively, the control device 190 can use the lane change controlfunction to reduce the object range in the adjacent lane in the traveldirection of the subject vehicle as the adjacent vehicle is nearer tothe subject vehicle lane side (as the distance in the road widthdirection from lane marks at the subject vehicle lane side of theadjacent lane to the adjacent vehicle is shorter).

In addition or alternatively, when the travel position of the adjacentvehicle in the road width direction is nearer to the opposite side tothe subject vehicle lane than the center of the adjacent lane, thecontrol device 190 can use the lane change control function to increasethe object range in the adjacent lane in the travel direction of thesubject vehicle. More specifically, the control device 190 uses the lanechange control function to increase the object range frontward withrespect to the subject vehicle when the adjacent vehicle travels aheadof the subject vehicle and increase the object range in the adjacentlane rearward with respect to the subject vehicle when the adjacentvehicle travels behind the subject vehicle. For example, in the exampleillustrated in FIGS. 17D-17F, provided that FIG. 17D represents theobject range in the adjacent lane before correction, the control device190 can use the lane change control function to increase the objectrange in the adjacent lane frontward when the adjacent vehicle travelsahead of the subject vehicle and nearer to the opposite side to thesubject vehicle lane as illustrated in FIG. 17E and increase the objectrange in the adjacent lane rearward when the adjacent vehicle travelsbehind the subject vehicle and nearer to the opposite side to thesubject vehicle lane as illustrated in FIG. 17F. In addition oralternatively, the control device 190 can use the lane change controlfunction to increase the object range in the adjacent lane in the traveldirection of the subject vehicle as the adjacent vehicle is nearer tothe opposite side to the subject vehicle lane (as the distance in theroad width direction from lane marks at the subject vehicle lane side ofthe adjacent lane to the adjacent vehicle is longer).

The control device 190 can use the lane change control function tocorrect the object range in the adjacent lane on the basis of thelighting state of winkers of the adjacent vehicle as illustrated inFIGS. 18A-18F instead of using the lane change control function tocorrect the required range on the basis of the lighting state of winkersof the adjacent vehicle as illustrated in FIGS. 14A-14F. Specifically,when the adjacent vehicle lights the winkers at the subject vehicle laneside, the control device 190 uses the lane change control function toreduce the length of the object range in the adjacent lane in the traveldirection of the subject vehicle thereby to reduce the object range inthe adjacent lane. More specifically, the control device 190 uses thelane change control function to reduce the object range in the adjacentlane from ahead when the adjacent vehicle traveling ahead of the subjectvehicle lights the winkers at the subject vehicle lane side and reducethe object range in the adjacent lane from behind when the adjacentvehicle traveling behind the subject vehicle lights the winkers at thesubject vehicle lane side. For example, in the example illustrated inFIGS. 18A-18C, provided that FIG. 18A represents the object range in theadjacent lane before correction, the control device 190 can use the lanechange control function to reduce the object range in the adjacent lanefrom ahead when the adjacent vehicle travels ahead of the subjectvehicle while lighting the winkers at the subject vehicle lane side asillustrated in FIG. 18B. When the adjacent vehicle travels behind thesubject vehicle while lighting the winkers at the subject vehicle laneside as illustrated in FIG. 18C, the control device 190 can use the lanechange control function to reduce the object range in the adjacent lanefrom behind.

In addition or alternatively, when the adjacent vehicle lights thewinkers at the opposite side to the subject vehicle lane, the controldevice 190 uses the lane change control function to increase the objectrange in the adjacent lane in the travel direction of the subjectvehicle. More specifically, the control device 190 uses the lane changecontrol function to increase the object range in the adjacent lanefrontward when the adjacent vehicle traveling ahead of the subjectvehicle lights the winkers at the opposite side to the subject vehiclelane and increase the object range rearward when the adjacent vehicletraveling behind the subject vehicle lights the winkers at the oppositeside to the subject vehicle lane. For example, in the exampleillustrated in FIGS. 18D-18F, provided that FIG. 18D represents theobject range in the adjacent lane before correction, the control device190 can use the lane change control function to increase the objectrange in the adjacent lane frontward when the adjacent vehicle travelsahead of the subject vehicle while lighting the winkers at the oppositeside to the subject vehicle lane as illustrated in FIG. 18E. When theadjacent vehicle travels behind the subject vehicle while lighting thewinkers at the opposite side to the subject vehicle lane as illustratedin FIG. 18F, the control device 190 can use the lane change controlfunction to increase the object range in the adjacent lane rearward.

The control device 190 can use the lane change control function tocorrect the object range in the adjacent lane on the basis of the speedand/or acceleration of the adjacent vehicle instead of using the lanechange control function to correct the required range on the basis ofthe speed and/or acceleration of the adjacent vehicle. Specifically, thecontrol device 190 uses the lane change control function to estimatewhether or not the adjacent vehicle comes away from the subject vehiclefrom the speed and acceleration of the adjacent vehicle. When theadjacent vehicle is estimated to come away from the subject vehicle, thecontrol device 190 uses the lane change control function to increase thelength of the object range in the adjacent lane in the travel directionof the subject vehicle thereby to increase the object range in theadjacent lane. More specifically, the control device 190 uses the lanechange control function to increase the object range in the adjacentlane frontward when the adjacent vehicle traveling ahead of the subjectvehicle comes away from the subject vehicle and increase the objectrange in the adjacent lane rearward behind when the adjacent vehicletraveling behind the subject vehicle comes away from the subjectvehicle.

In addition or alternatively, when the adjacent vehicle comes close tothe subject vehicle, the control device 190 uses the lane change controlfunction to reduce the length of the object range in the adjacent lanein the travel direction of the subject vehicle thereby to reduce theobject range in the adjacent lane in the travel direction of the subjectvehicle. More specifically, the control device 190 uses the lane changecontrol function to reduce the object range in the adjacent lane fromahead when the adjacent vehicle traveling ahead of the subject vehiclecomes close to the subject vehicle and reduce the object range in theadjacent lane from behind when the adjacent vehicle traveling behind thesubject vehicle comes close to the subject vehicle.

The following process will be described on the assumption that therequired range is corrected in step S111.

In step S112, the control device 190 uses the lane change controlfunction to determine whether or not there is a space within the objectrange in the adjacent lane after the predetermined time T1. The spacecorresponds to the required range corrected in step S111. The objectrange in the adjacent lane after the predetermined time T1 is estimatedin step S107. Specifically, as illustrated in FIG. 19A, the controldevice 190 uses the lane change control function to set the corrected,required range at the target position for lane change which is set instep S105. Then, the control device 190 uses the lane change controlfunction to determine whether or not the object range in the adjacentlane after the predetermined time T1 includes the corrected, requiredrange. For example, in the example illustrated in FIG. 19A, the objectrange in the adjacent lane after the predetermined time T1 does notinclude the corrected, required range. The control device 190 thereforeuses the lane change control function to determine that there is not aspace corresponding to the corrected, required range within the objectrange in the adjacent lane after the predetermined time T1. On the otherhand, when the object range in the adjacent lane after the predeterminedtime T1 includes the corrected, required range, the control device 190uses the lane change control function to determine that there is a spacecorresponding to the corrected, required range within the object rangein the adjacent lane after the predetermined time T1. When there is aspace corresponding to the corrected, required range within the objectrange in the adjacent lane after the predetermined time T1, the routineproceeds to step S114 illustrated in FIG. 4 while when there is nospace, the routine proceeds to step S113.

In step S113, it has been determined that the object range in theadjacent lane after the predetermined time T1 does not include thecorrected, required range and a space cannot be detected whichcorresponds to the required range within the object range in theadjacent lane after the predetermined time T1. In step S113, therefore,the control device 190 uses the lane change control function to changethe target position for lane change. Specifically, the control device190 uses the lane change control function to re-set the target positionfor lane change so that the object range in the adjacent lane after thepredetermined time T1 includes the corrected, required range. Forexample, when the front portion of the required range is not included inthe object range in the adjacent lane after the predetermined time T1 asillustrated in FIG. 19A, the target position for lane change is shiftedrearward. This allows the corrected, required range to be included inthe object range in the adjacent lane after the predetermined time T1 asillustrated in FIG. 19B, and it is determined that a space can bedetected which corresponds to the required range within the object rangein the adjacent lane after the predetermined time T1. Step S113 isfollowed by step S106 from which detection of the object range and thelike are performed again.

On the other hand, when, in step S112, it is determined that the objectrange in the adjacent lane after the predetermined time T1 includes thecorrected, required range, the routine proceeds to step S114 illustratedin FIG. 4. In step S114, the control device 190 uses the lane changecontrol function to perform a query process for the lane change control.The lane change control refers to control for executing lane change. Instep S114, a query as to whether or not the lane change control shouldbe executed is made to the driver before the lane change is actuallyperformed. Then, in step S115, a determination is made whether or notthe driver permits the lane change in response to the query of stepS114. When the driver permits the lane change, the routine proceeds tostep S116 while when the driver does not permit the lane change, theroutine returns to step S101.

For example, in step S104, the control device 190 can use the lanechange control function to display a message “Which action do you selectfor the preceding vehicle?” together with query information on thedisplay of the announcement device 150. The query information mayinclude options of “Follow” and “Change lanes to overtake.” In responseto this, the driver can select any of the options via the input device160. For example, when the driver selects the option of “Change lanes toovertake,” the lane change control function is used in step S115 todetermine that the driver permits the lane change, and the routineproceeds to step S116. On the other hand, when the driver selects theoption of “Follow,” the lane change control function is used in stepS115 to determine that the driver does not permit the lane change, andthe routine returns to step S101.

The control device 190 can also use the lane change control function topresent a message “Which action do you select for the precedingvehicle?” together with options of “Follow” and “Change lanes toovertake” as query information and announce the query information to thedriver such that the query information further includes a message“Selection will be automatically performed unless a select button ispressed within X seconds.” In this case, when the driver does not selectany of the options within a certain period of time, the control device190 can use the lane change control function to automatically select apredetermined default option among the options of “Follow” and “Changelanes to overtake.” The default option may be a specific option or mayalso be an option that can be variably set. For example, when the objectrange becomes small in the certain period of time until the defaultoption is selected, the control device 190 can use the lane changecontrol function to set “Follow” as the default option while when theobject range becomes large, the control device 190 can use the lanechange control function to set “Change lanes to overtake” as the defaultoption. The control device 190 can also use the lane change controlfunction to set an option which the driver has selected many times inpast times as the default option on the basis of the history ofselection of options by the driver. When the driver selects the optionof “Change lanes to overtake” within the certain period of time, theroutine proceeds to step S116 while when the driver selects the optionof “Follow” within the certain period of time, the routine returns tostep S101.

The control device 190 can also use the lane change control function toannounce messages, such as “Now changing lanes to overtake the precedingvehicle” and “Please press the cancel button below if discontinuing thelane change,” together with query information including a “Cancel”button for canceling the lane change to the driver via the announcementdevice 150. In this case, it is assumed that, after the queryinformation is announced in step S114, the driver permits the lanechange in step S115, and the routine proceeds to step S117. Then, instep S117, the lane change control is initiated. When the driver pressesthe “Cancel” button, the lane change control is canceled and the routinereturns to step S101.

In step S116, the control device 190 uses the lane change controlfunction to acquire the time limit for lane change. In the presentembodiment, as illustrated in FIG. 2, the table stores the time for thesubject vehicle to approach a point at which lane change is difficult ineach travel scene, as the time limit. The control device 190 uses thelane change control function to refer to the table illustrated in FIG. 2to acquire the time limit (Z) in the travel scene of the subjectvehicle. For example, in the “scene of catching up with a precedingvehicle” among the examples illustrated in FIG. 2, the time limit isstored as (time-to-contact with the preceding vehicle—α) seconds. Inthis case, the control device 190 uses the travel control function torefer to the table illustrated in FIG. 2 to calculate thetime-to-contact (TTC) with the preceding vehicle and acquire (thecalculated time-to-contact (TTC) with the preceding vehicle—α) secondsas the time limit. The constant α is some seconds (e.g. 5 seconds) andcan be appropriately set for each travel scene. For example, when thetime-to-contact (TTC) with the preceding vehicle is 30 seconds and α is5 seconds, the time limit for lane change is 25 seconds.

In step S117, the control device 190 uses the lane change controlfunction to initiate the lane change control. Specifically, the controldevice 190 uses the lane change control function to allow the drivecontrol device 180 to initiate control of the operation of the steeringactuator so that the subject vehicle moves to the target position forlane change set in step S105 or step S113.

In steps S118 to S122, as in steps S104 and S106 to S109, the currentobject range and the object range after a required time T2 for thesubject vehicle to move to the target position are detected (steps S118to S120) and estimation is made whether the object range becomes smallafter the predetermined time T2 (step S121). When the object range isestimated to become small after the predetermined time T2 (stepS121=Yes), the announcement information that the object range willbecome small is announced to the driver (step S122).

Then, in step S123, the control device 190 uses the lane change controlfunction to determine whether or not there is a space within the objectrange in the adjacent lane after the predetermined time T2. The spacecorresponds to the required range corrected in step S111. The objectrange in the adjacent lane after the predetermined time T2 is estimatedin step S120. The control device 190 uses the lane change controlfunction to set the corrected, required range at the target position forlane change. When the object range in the adjacent lane after thepredetermined time T2 includes the corrected, required range, thecontrol device 190 uses the lane change control function to determinethat there is a space corresponding to the required range within theobject range in the adjacent lane after the predetermined time T2, andthe routine proceeds to step S124. On the other hand, when adetermination is made that there is not a space corresponding to therequired range within the object range in the adjacent lane after thepredetermined time T2, the routine proceeds to step S128.

In step S124, the control device 190 uses the lane change controlfunction to determine whether or not the time limit Z acquired in stepS117 has passed after initiating the lane change control in step S116.When the elapsed time S1 after initiating the lane change controlexceeds the time limit Z, the routine proceeds to step S127 while whenthe elapsed time S1 after initiating the lane change control does notexceed the time limit Z, the routine proceeds to step S125.

In step S125, the control device 190 uses the lane change controlfunction to determine whether or not the subject vehicle has reached thetarget position for lane change. When the subject vehicle has reachedthe target position for lane change, the lane change control is finishedin step S126 to complete the lane change control process. Thus, the lanechange of the subject vehicle is completed. On the other hand, when thesubject vehicle has not reached the target position for lane change, theroutine returns to step S118 to continue the lane change control.

When, in step S124, the elapsed time S1 after initiating the lane changecontrol exceeds the time limit Z, that is, when the subject vehiclecannot reach the target position for lane change even after the timelimit Z has passed after initiating the lane change control, the routineproceeds to step S127. In step S127, the control device 190 uses thelane change control function to perform a discontinuation process forthe lane change control. Specifically, the control device 190 uses thelane change control function to announce the information that the lanechange control will be discontinued to the driver. For example, thecontrol device 190 can use the lane change control function to announcea message “Lane change will be discontinued due to time out” to thedriver via the announcement device 150. Thereafter, the lane changecontrol function is finished in step S126 and the routine returns tostep S101. In the discontinuation process for the lane change control,the control device 190 may use the lane change control function to leavethe travel position of the subject vehicle in the road width directionat the position when finishing the lane change control or recover thetravel position to the position when initiating the lane change control.When the travel position is recovered to the position when initiatingthe lane change control, a message such as “The original position willbe recovered due to time out” may be announced to the driver.

In the discontinuation process for the lane change control, the controldevice 190 can use the lane change control function to determine whetherthe driver desires to continue the lane change while maintaining thecurrent travel state. When the driver desires to continue the lanechange, the time limit Z may be extended. For example, the controldevice 190 can use the lane change control function to present someannouncement information to the driver. The announcement information mayinclude a message “Continue lane change despite time out?” and optionsof “Discontinue” and “Continue.” When the driver selects the option of“Continue,” the control device 190 uses the lane change control functionto elongate the time limit Z, and the routine returns to step S118. Whenthe driver selects the option of “Discontinue,” the lane change controlis finished in step S126.

The control device 190 may use the lane change control function toprovide a time for response when determining whether the driver desiresto continue the lane change and automatically execute the default optionif the driver does not make a response within the time for response. Forexample, the query information can be announced to the driver, includinga message “Selection will be automatically performed unless a selectbutton is pressed within XX seconds” in addition to a message “Continuelane change despite time out?” and options of “Discontinue” and“Continue.” The time for response and the default option may be aspecific time and a specific option or may also be variably set. In anexample in which the time for response and the default option arevariably set, the time for response can be reduced or “Discontinue” canbe set as the default option when the object range becomes small. Inaddition or alternatively, the history of selection by the driver may beused to reduce the time for response to an option which the driver hasselected few times in past times or set an option which the driver hasselected many times in past times as the default option. When the optionof “Continue” is selected, the time limit Z is elongated and the routinethen returns to step S118 while when the option of “Discontinue” isselected, the lane change control is finished in step S126.

In the discontinuation process for the lane change control, the controldevice 190 can also use the lane change control function toautomatically continue the lane change and announce a method ofdiscontinuing the lane change to the driver. For example, the controldevice 190 can use the lane change control function to announcemessages, such as “Lane change will be continued despite time out” and“Please press the cancel button below if discontinuing the lane change,”together with announcement information including a “Cancel” button forcanceling the lane change to the driver via the announcement device 150.In this case, when the “Cancel” button is not pressed, the time limit Zis elongated and the routine then returns to step S118. When the“Cancel” button is pressed, the lane change control is finished in stepS126.

In the discontinuation process for the lane change control, when thetime limit Z is elongated to continue the lane change, the time limit Zis elongated within a time in which the lane change can be continued.For example, provided that the travel scene of the subject vehicle is a“scene of approaching a merging point,” when the time for arriving atthe merging point is 10 seconds but the time limit Z is 7 seconds, thatis, when the time for arriving at the merging point exceeds the timelimit Z, the control device 190 can use the lane change control functionto elongate the time limit Z, for example, up to 9 seconds to continuethe lane change. In this case, if the elongated time limit Z (9 seconds)passes, the lane change control will be finished.

Thus, when the elapsed time S1 after initiating the lane change controlexceeds the time limit Z, the discontinuation process for the lanechange control can be performed thereby to effectively preventuncomfortable feeling given to the driver. This will be morespecifically described. For example, if the lane change is not performedeven when the time limit Z has passed after initiating the lane changecontrol, the intention of the driver to change lanes may disappear. Insuch a case, uncomfortable feeling may be given to the driver if thelane change is performed after the driver has changed mind so as not todesire lane change or if the lane change is performed when the driverforgets it. The discontinuation process for the lane change control canmitigate such uncomfortable feeling given to the driver.

In step S123, when a determination is made that there is not a spacecorresponding to the required range within the object range in theadjacent lane after the predetermined time T2, the routine proceeds tostep S128. That is, when there was a space corresponding to the requiredrange within the object range in the adjacent lane at the time point ofstep S112 of initiating the lane change control but there is not a spacecorresponding to the required range within the object range in theadjacent lane after initiating the lane change control, the routineproceeds to step S128. In step S123, also when the object range in theadjacent lane at the time point of step S112 of initiating the lanechange control becomes small at the time point of step S123, the routinemay proceed to step S128. In step S128, detection is performed for thepositional relationship in the road width direction between the subjectvehicle and lane marks which the subject vehicle will get across whenchanging lanes (referred to as “object lane marks,” hereinafter).

For example, FIGS. 20A-20D exemplify a scene in which the subjectvehicle changes lanes in the direction represented by arrows in thefigure (lane change from the left-side lane to the right-side lane inthe figure). In this case, the control device 190 uses the lane changecontrol function to determine any of a state in which no part of thesubject vehicle gets across the object lane marks as illustrated in FIG.20A, a state in which a part of the subject vehicle gets across theobject lane marks but the center line of the subject vehicle does notget across the object lane marks as illustrated in FIG. 20B, a state inwhich the whole of the subject vehicle does not completely get acrossthe object lane marks but the center line of the subject vehicle getsacross the object lane marks as illustrated in FIG. 20C, and a state inwhich the whole of the subject vehicle gets across the object lane marksas illustrated in FIG. 20D.

In step S129, the control device 190 uses the lane change controlfunction to perform a control process for discontinuing or continuingthe lane change, on the basis of the positional relationship in the roadwidth direction between the object lane marks and the subject vehicledetermined in step S128. Specifically, the control device 190 uses thelane change control function to determine (a) a method of presentinginformation to the driver when discontinuing or continuing lane change,(b) control after discontinuing or continuing lane change, and (c) atravel position of the subject vehicle when discontinuing or continuinglane change, on the basis of the positional relationship in the roadwidth direction between the object lane marks and the subject vehicle.

For example, the control device 190 can use the lane change controlfunction to carry out any of the following four methods as the method(a) of presenting information to the driver when discontinuing orcontinuing lane change: (a1) a method that includes presentinginformation for allowing the driver to select between options ofdiscontinuing and continuing lane change without time limit and, whenthe driver selects any of the options, executing the option(discontinuing or continuing lane change) selected by the driver; (a2) amethod that includes presenting information for allowing the driver toselect between options of discontinuing and continuing lane change withtime limit and, when the driver selects any of the options within thetime limit, executing the option (discontinuing or continuing lanechange) selected by the driver or, when the driver does not select boththe options within the time limit, executing control (default control)of a predetermined option among the options of discontinuing andcontinuing lane change; (a3) a method that includes automaticallyexecuting discontinuation or continuation of lane change and expresslyproviding the driver with a method of canceling the discontinuation orcontinuation of lane change which is automatically executed; and (a4) amethod that includes automatically executing discontinuation orcontinuation of lane change without expressly providing the driver witha method of canceling the discontinuation or continuation of lane changewhich is automatically executed.

The control device 190 can also use the lane change control function tocarry out any of the following three control schemes as (b) controlcontents after discontinuing or continuing lane change: (b1) a schemethat includes discontinuing the lane change and also discontinuing theautomatic travel control; (b2) a scheme that includes discontinuing onlythe lane change control and continuing the automatic travel control; and(b3) a scheme that includes suspending the lane change control into awaiting state until a space corresponding to the required range isdetected again within the object range in the adjacent lane and resumingthe lane change control when a space corresponding to the required rangeis detected again within the object range in the adjacent lane.

The control device 190 can further use the lane change control functionto carry out any of the following three positional adjustment schemesfor the travel position (c) of the subject vehicle when discontinuing orcontinuing the lane change control: (c1) a scheme that includesrecovering the position of the subject vehicle to the original positionbefore initiating the lane change; (c2) a scheme that includes movingthe subject vehicle to a position in the vicinity of the object lanemarks in the lane in which the subject vehicle traveled beforeinitiating the lane change; and (c3) a scheme that includes maintainingthe current position.

The control device 190 can use the lane change control function toperform the control process for discontinuing or continuing lane changeby appropriately combining two or more of the method (a) of presentinginformation to the driver when discontinuing or continuing lane change,(b) control contents after discontinuing or continuing lane change, and(c) a travel position of the subject vehicle when discontinuing orcontinuing lane change, on the basis of the positional relationship inthe road width direction between the object lane marks and the subjectvehicle.

For example, when no part of the subject vehicle gets across the objectlane marks as illustrated in FIG. 20A, the control device 190 can usethe lane change control function to carry out the method (a4) thatincludes automatically executing discontinuation of lane change withoutexpressly providing the driver with a method of canceling thediscontinuation of lane change. In this case, the control device 190 canuse the lane change control function to carry out the scheme (b1) thatincludes discontinuing the lane change and also discontinuing theautomatic travel control and the scheme (c1) that includes recoveringthe position of the subject vehicle to the original position beforeinitiating the lane change. In such a case, the control device 190 canuse the lane change control function to announce the control contents tobe performed from that time to the driver, such as “Position will berecovered to the original position because the space for lane change maybe insufficient” and “Automatic travel control will be canceled afterrecovery to the original position.” In this case, the process proceedsto step S126 to finish the lane change control.

When a part of the subject vehicle gets across the object lane marks butthe center line of the subject vehicle does not get across the objectlane marks as illustrated in FIG. 20B, the control device 190 can usethe lane change control function to carry out the method (a3) thatincludes automatically executing discontinuation of lane change andexpressly providing the driver with a method of canceling thediscontinuation of lane change. In this case, the control device 190 canuse the lane change control function to carry out the scheme (c2) thatincludes moving the subject vehicle to a position in the vicinity of theobject lane marks in the lane in which the subject vehicle traveledbefore initiating the lane change and then carry out the scheme (b2)that includes discontinuing only the lane change control and continuingthe automatic travel control. In such a case, the control device 190 canuse the lane change control function to announce the control contents tobe performed from that time to the driver, such as “Position will berecovered into the original lane because the space for lane change maybe insufficient” and “Previous automatic travel control will becontinued after recovery to the original position.” In addition oralternatively, the control device 190 can use the lane change controlfunction to display a message “Please press the button below if lanechange should be continued” together with a button for continuing thelane change. When the driver presses the button for continuing lanechange, the process proceeds to step S130 while when the driver does notpress the button for continuing lane change, the process proceeds tostep S126.

When the whole of the subject vehicle does not completely get across theobject lane marks but the center line of the subject vehicle gets acrossthe object lane marks, for example, as illustrated in FIG. 20C, thecontrol device 190 can use the lane change control function to carry outthe method (a4) that includes automatically executing continuation oflane change without expressly providing the driver with a method ofcanceling the continuation of lane change. In this case, the controldevice 190 can use the lane change control function to carry out thescheme (c3) that includes waiting while maintaining the travel positionof the subject vehicle at the current position and the scheme (b3) thatincludes suspending the lane change control until a space correspondingto the required range is detected again within the object range in theadjacent lane and resuming the lane change control when a spacecorresponding to the required range is detected again within the objectrange in the adjacent lane. In this case, for example, the controldevice 190 can use the lane change control function to announce thecontrol contents to be performed from that time to the driver, such as“Waiting will be conducted at the current position because the space forlane change may be insufficient” and “Lane change control will beresumed if a space for lane change is found.” In this case, the processproceeds to step S130.

When the whole of the subject vehicle gets across the object lane marks,for example, as illustrated in FIG. 20D, the control device 190 can usethe lane change control function to carry out the method (a4) thatincludes automatically executing discontinuation of lane change withoutexpressly providing the driver with a method of canceling thediscontinuation of lane change. In this case, the control device 190 canuse the lane change control function to carry out the scheme (c3) thatincludes maintaining the travel position of the subject vehicle at thecurrent position and the scheme (b2) that includes discontinuing onlythe lane change control and continuing the automatic travel control. Inthis case, for example, the control device 190 can use the lane changecontrol function to announce the control contents to be performed fromthat time to the driver, such as “Waiting will be conducted at thecurrent position because the space for lane change may be insufficient”and “Previous automatic travel control will be continued.” In this case,the process proceeds to step S126 to finish the lane change control.

The positional relationship in the road width direction between theobject lane marks and the subject vehicle is not limited to the fourscenes illustrated in FIGS. 20A to 20D and five or more or three or lesspossible scenes may be employed. The combination of control schemes foreach positional relationship is not limited to the above-describedcombinations. Any combination is possible among two or more of themethod (a) of presenting information to the driver when discontinuing orcontinuing lane change, (b) control contents after discontinuing orcontinuing lane change, and (c) a travel position of the subject vehiclewhen discontinuing or continuing lane change.

Description will then be made for a case in which continuation of lanechange is executed in step S129. Step S129 of initiating thecontinuation of lane change is followed by step S130. In step S130, thecontrol device 190 uses the lane change control function to measure anelapsed time S2 after the lane change control comes to a waiting statein step S129. That is, in the present embodiment, when the lane changeis continued in step S129, the lane change is suspended and the lanechange control comes to a waiting state until a space corresponding tothe required range is detected again in the object range in the adjacentlane. In step S130, the elapsed time S2 after initiating the waiting ofthe lane change control in this manner is measured.

In step S131, the control device 190 uses the lane change controlfunction to estimate a required time T3 for the subject vehicle to movefrom the current position to the target position for lane change. Therequired time T3 can be estimated as in step S106.

In step S132, the control device 190 uses the lane change controlfunction to determine whether or not the total time (S2+T3) of theelapsed time S2 measured in step S130 and the required time T3 estimatedin step S131 exceeds the time limit Z acquired in step S118. When thetotal time (S2+T3) exceeds the time limit Z, the routine proceeds tostep S133 in which the control device 190 uses the lane change controlfunction to cancel the waiting state of the lane change control and movethe subject vehicle to the travel position of the subject vehicle beforeinitiating the lane change. Step S133 is followed by step S126 in whichthe lane change control is finished. On the other hand, when the totaltime (S2+T3) does not exceed the time limit Z, the routine proceeds tostep S134.

In step S134, the control device 190 uses the lane change controlfunction to continue the waiting state of the lane change control. StepS134 is followed by steps S135 to S138 in which, as in steps S104 andS106 to S109, the current object range and the object range after therequired time T3 are detected (steps S135 and S136) and estimation ismade whether or not the object range becomes small after thepredetermined time T3 (step S137). When the object range is estimated tobecome small after the predetermined time T3 (step S137=Yes), theannouncement information that the object range will become small isannounced to the driver (step S138).

In step S139, as in step S123, a determination is made whether or notthere is a space within the object range in the adjacent lane after thepredetermined time T3. The space corresponds to the required rangecorrected in step S111. The object range in the adjacent lane after thepredetermined time T3 is estimated in step S136. The control device 190uses the lane change control function to set the corrected, requiredrange at the target position for lane change. When the object range inthe adjacent lane after the predetermined time T3 includes thecorrected, required range, the control device 190 uses the lane changecontrol function to determine that there is a space corresponding to therequired range within the object range in the adjacent lane after thepredetermined time T3, and the routine proceeds to step S140. In stepS140, the control device 190 uses the lane change control function tocancel the waiting state of the lane change control and resume the lanechange control because a space corresponding to the required range isdetected within the object range in the adjacent lane. The process thenreturns to step S118. On the other hand, when a determination is madethat there is not a space corresponding to the required range within theobject range in the adjacent lane after the predetermined time T3, theroutine proceeds to step S141 in which the waiting state of the lanechange control is continued, and the routine then returns to step S130.

As described above, when determining whether or not to permit lanechange, the travel control apparatus 100 according to the presentembodiment sets a range as a required range at a target position forlane change. The range has a size equal to or larger than the size of arange which the subject vehicle occupies on a road surface. The travelcontrol apparatus 100 also detects a range in which no obstacles existat the timing when the subject vehicle completes the lane change, as anobject range. Then, when the object range in the adjacent lane includesthe required range, the travel control apparatus 100 determines that aspace to which the subject vehicle can change lanes exists in theadjacent lane, and permits the lane change. Thus, in the presentembodiment, the object range in which no obstacles exist at the timingwhen the subject vehicle completes the lane change and the requiredrange necessary for the subject vehicle to change lanes are comparedthereby to allow a determination to be appropriately made as to whetheror not lane change should be performed.

Moreover, in the present embodiment, when the object range in theadjacent lane and the required range are compared to detect a spacecorresponding to the required range within the object range in theadjacent lane, correction is performed to reduce the required range orincrease the object range in the adjacent lane, as illustrated in FIGS.11A and 11B, in a case in which the necessity level of lane change inthe travel scene of the subject vehicle is high (the necessity level oflane change is a predetermined value st1 or higher) as compared with acase in which the necessity level of lane change in the travel scene ofthe subject vehicle is low (the necessity level of lane change is lowerthan the predetermined value st1). Through this operation, when thetravel scene of the subject vehicle is a travel scene that is suitablefor lane change, lane change can be readily permitted. Thus, adetermination of whether lane change should be performed can beappropriately performed in accordance with the travel scene of thesubject vehicle.

Furthermore, in the present embodiment, when a space corresponding tothe required range is detected within the object range in the adjacentlane, correction is performed to increase the required range or reducethe object range in the adjacent lane in a case in which the necessitylevel of lane change in the travel scene of the subject vehicle is low(the necessity level of lane change is lower than a predetermined valuest2 (st1>st2)) as compared with a case in which the necessity level oflane change in the travel scene of the subject vehicle is high (thenecessity level of lane change is the predetermined value st2 orhigher). Through this operation, when the subject vehicle comes close tothe adjacent vehicle during lane change in a scene in which thenecessity level of lane change is low, the lane change is brought undercontrol. Thus, a determination of whether lane change should beperformed can be more appropriately performed in accordance with thetravel scene.

In the present embodiment, as illustrated in FIG. 2, the table fordetermining the travel scene preliminarily stores determinationconditions for travel scenes that are suitable for lane change and thenecessity level of lane change in each travel scene. Through thisconfiguration, in the present embodiment, it is possible to determinethe travel scene of the subject vehicle with reference to the tableillustrated in FIG. 2 and appropriately acquire the necessity level oflane change in the travel scene of the subject vehicle.

<<Second Embodiment>>

Next, the travel control apparatus according to a second embodiment ofthe present invention will be described. The travel control apparatus100 according to the second embodiment has the same configuration asthat of the travel control apparatus 100 according to the firstembodiment and operates in the same manner as in the first embodimentexcept that the travel control apparatus 100 operates as describedbelow. Specifically, in the second embodiment, the travel controlapparatus 100 performs a lane change control process illustrated in FIG.21 as substitute for the lane change control process illustrated in FIG.5.

This will be more specifically described. When, in step S123 illustratedin FIG. 4, a determination is made that a space corresponding to therequired range cannot be detected within the object range in theadjacent lane after the predetermined time T2, the routine proceeds tostep S201 illustrated in FIG. 21. In step S201, the control device 190uses the lane change control function to initiate a lane change requestcontrol for slowly bringing the subject vehicle close to the targetposition for lane change. The lane change request control is controlthat includes slowly bringing the subject vehicle close to the targetposition for lane change so that the driver of another vehicle enteringthe object range in the adjacent lane perceives that the subject vehiclewill change lanes, asking for the drive of the other vehicle to providea lane change space that includes the target position for lane change,and allowing the subject vehicle to change lanes. In the lane changerequest control, the control device 190 uses the lane change controlfunction to move the subject vehicle in the road width direction at alower speed than that when performing ordinary lane change. For example,the control device 190 can use the lane change control function to movethe subject vehicle in the road width direction at half speed ascompared with the case of changing lanes, thereby to slowly bring thesubject vehicle close to the target position for lane change.

In step S201, the control device 190 can use the lane change controlfunction to change the moving speed of the subject vehicle in the roadwidth direction by taking into account a degree that the corrected,required range deviates from the object range after the predeterminedtime T2. For example, when the degree that the corrected, required rangedeviates from the object range after the predetermined time T2 is apredetermined value or more, the control device 190 can use the lanechange control function to change the moving speed of the subjectvehicle in the road width direction to a lower speed than the speed whenthe degree is less than the predetermined value. When the degree thatthe corrected, required range deviates from the object range after thepredetermined time T2 is large, another vehicle is highly likely toenter the target position for lane change of the subject vehicleaccordingly. In such a case, if the subject vehicle is brought close tothe target position for lane change, the driver is liable to feelanxious. Such anxious feeling of the driver to another vehicle cantherefore be mitigated by reducing the moving speed of the subjectvehicle in the road width direction (i.e. by more slowly bringing thesubject vehicle close to the target position for lane change).

In addition or alternatively, in step S201, the control device 190 canuse the lane change control function to change the moving speed of thesubject vehicle in the road width direction in accordance with thepositional relationship between the object lane marks and the subjectvehicle detected in step S128. For example, in a state in which thecenter line of the subject vehicle gets across the lane marks asillustrated in FIG. 20C, the control device 190 can use the lane changecontrol function to reduce the moving speed of the subject vehicle inthe road width direction. This operation can mitigate the anxiousfeeling of the driver even when the subject vehicle is moved to thetarget position for lane change in a state in which the subject vehicleand another vehicle are close to each other so that they may come closerto each other. In addition or alternatively, in a state in which thecenter line of the subject vehicle gets across the lane marks, thecontrol device 190 can use the lane change control function to make themoving speed “0,” that is, to maintain the position of the subjectvehicle in the road width direction (i.e. to wait at the currentposition) rather than varying the position. This can mitigate theanxious feeling of the driver because the subject vehicle does not comeclose to the other vehicle.

Processes in steps S202 to S205 are the same as those in steps S135 toS138, so the description will be omitted. Then, in step S206, thecontrol device 190 uses the lane change control function to determinewhether or not the distance between the subject vehicle and the othervehicle becomes a predetermined distance or less as a result of the lanechange request control performed in step S201 for slowly bringing thesubject vehicle close to the adjacent vehicle. The distance between thesubject vehicle and the other vehicle as used in this case may be adirect distance or a distance in the road width direction. When thedistance between the subject vehicle and the other vehicle is largerthan the predetermined distance, the routine proceeds to step S207 inwhich the control device 190 uses the lane change control function todetermine whether or not the subject vehicle has arrived at the targetposition for lane change. When the subject vehicle has not arrived atthe target position for lane change, the routine returns to step S202 tocontinue the lane change request control. When the subject vehicle hasarrived at the target position for lane change, the routine returns tostep S126 to finish the lane change control.

When, in step S206, a determination is made that the distance betweenthe subject vehicle and the other vehicle becomes the predetermineddistance or less, the routine proceeds to step S208. In step S208, thecontrol device 190 uses the lane change control function to cancel thelane change request control initiated in step S201 and the routine thenproceeds to step S126 to cancel the lane change control. Even when thesubject vehicle is brought close to the target position for lane change,the driver of the other vehicle may not necessarily provide a spacenecessary for lane change and the subject vehicle may come close to theother vehicle to some extent. In such a case, the lane change requestcontrol can be canceled thereby to allow the subject vehicle to travelin safety.

In step S206, the control device 190 can also use the lane changecontrol function to set the above predetermined distance variable inaccordance with the “necessity level of lane change” in the scene inwhich the subject vehicle travels. For example, when the “necessitylevel of lane change” in the travel scene of the subject vehicle is high(the necessity level is a predetermined value or more), the controldevice 190 can use the lane change control function to reduce the abovepredetermined distance as compared with a case in which the “necessitylevel of lane change” in the travel scene of the subject vehicle is low(the necessity level is less than the predetermined value). This allowsthe subject vehicle to come closer to the target position for lanechange in a travel scene in which the “necessity level of lane change”is high. Accordingly, the adjacent vehicle can be informed of theintention that the subject vehicle will change lanes, and the lanechange to the adjacent lane can be readily performed.

As described above, in the second embodiment, when a space correspondingto the required range cannot be detected in the object range in theadjacent lane, the lane change request control is performed to slowlybring the subject vehicle close to the target position for lane change.This allows the driver of the adjacent vehicle to be informed of theintention of lane change of the subject vehicle even when a spacecorresponding to the required range cannot be detected in the objectrange in the adjacent lane. As a result, the driver of the adjacent lanemay provide a space necessary for lane change of the subject vehicle andthe lane change may thus be appropriately performed.

Embodiments heretofore explained are described to facilitateunderstanding of the present invention and are not described to limitthe present invention. It is therefore intended that the elementsdisclosed in the above embodiments include all design changes andequivalents to fall within the technical scope of the present invention.

For example, in the above-described one or more embodiments of thepresent invention, a configuration is exemplified in which the requiredrange is compared with the object range in the adjacent lane at thetiming when the subject vehicle completes lane change, but the presentinvention is not limited to this configuration and another configurationcan also be employed in which, for example, the required range iscompared with the object range in the adjacent lane at the present time.

In the above-described one or more embodiments of the present invention,a configuration is exemplified in which, when the travel scene of thesubject vehicle corresponds to a plurality of travel scenes illustratedin FIG. 2, the travel scene in which the necessity level of lane changeis highest is determined as the travel scene of the subject vehicle andlane change is performed in the “direction of lane change” in the travelscene, but the present invention is not limited to this configurationand another configuration can also be employed in which, for example,when the travel scene of the subject vehicle corresponds to a pluralityof travel scenes illustrated in FIG. 2, the “direction of lane change”in each travel scene is specified as the right direction or the leftdirection and lane change is performed in the right direction if the“direction of lane change” is the right direction in a larger number oftravel scenes while lane change is performed in the left direction ifthe “direction of lane change” is the left direction in a larger numberof travel scenes.

In the above-described one or more embodiments of the present invention,a configuration is exemplified in which the time limit Z for each travelscene is stored in the table as illustrated in FIG. 2, but the presentinvention is not limited to this configuration and another configurationcan also be employed in which the time limit Z is calculated, forexample, on the basis of the necessity level of lane change stored inthe table illustrated in FIG. 2. In this case, the time limit Z may beset longer as the necessity level of lane change is higher. Stillanother configuration may also be employed in which a specific time foreach travel scene is stored as the time limit Z in the table.

In the above-described one or more embodiments of the present invention,a configuration is exemplified in which a range with no obstacles in theadjacent lane is detected as the object range and a range with noobstacles in the next adjacent lane is also detected as the object rangeas illustrated in FIG. 6C, but the present invention is not limited tothis configuration and another configuration can also be employed inwhich, for example, the range with no obstacles in the adjacent lane isdetected as a first object range while the range with no obstacles inthe next adjacent lane is detected as a second object range so that theobject range in the adjacent lane and the object range in the nextadjacent lane are separately detected.

In the above-described one or more embodiments of the present invention,a configuration is exemplified in which the required range is reduced orthe object range in the adjacent lane is increased when the necessitylevel of lane change is high in the travel scene of the subject vehicle,but another configuration can also be employed in which, for example,even when the necessity level of lane change in the travel scene of thesubject vehicle is high, the required range is increased or the objectrange in the adjacent lane is reduced in at least one case among a casein which the adjacent lane is obstructed ahead, a case in which anemergency vehicle is approaching, a case in which a parking vehicleexists ahead in the adjacent lane, a case in which the vehicle speed ofthe adjacent vehicle traveling ahead in the adjacent lane is lower thanthe vehicle speed of the subject vehicle, and a case in which thevehicle speed of the adjacent vehicle traveling behind in the adjacentlane is higher than the vehicle speed of the subject vehicle. In such ascene that is not suitable for lane change, the required range isincreased or the object range in the adjacent lane is reduced and it isthereby possible to more appropriately determine whether or not lanechange should be performed, in accordance with the travel scene.

In the above-described second embodiment, a configuration is exemplifiedin which the lane change request control is performed for slowlybringing the subject vehicle close to the target position for lanechange, but the present invention is not limited to this configurationand another configuration may also be employed in which, for example,the lane change request control is performed for slowly bringing thesubject vehicle close to the adjacent lane. Also in this case, thedriver of the adjacent vehicle can be informed of the intention of lanechange of the subject vehicle, and a space necessary for lane change maythus be ensured.

The sensors 110 in the above-described embodiments correspond to thefirst detector and second detector of the present invention and thecontrol device 190 corresponds to the travel control apparatus of thepresent invention.

REFERENCE SIGNS LIST

-   100 Travel control apparatus-   110 Sensors-   120 Subject vehicle position detection device-   130 Map database-   140 Onboard equipment-   150 Announcement device-   160 Input device-   170 Communication device-   180 Drive control device-   190 Control device

The invention claimed is:
 1. A travel control method executed by atravel control apparatus, the travel control apparatus comprising: afirst detector configured to detect an obstacle around a subject vehicletraveling in a first lane; and a second detector configured to detect asecond lane adjacent to the first lane, the travel control apparatusbeing configured to: set a first range at a target position for lanechange in the second lane, the first range having a size equal to orlarger than a size which the subject vehicle occupies on a road surface;detect a range in the second lane as a second range, the range in thesecond lane being located at a side of the subject vehicle, the obstaclebeing absent in the range in the second lane; and permit the subjectvehicle to change lanes when the second range includes the first range,the travel control method comprising: a first step of determining atravel scene of the subject vehicle on a basis of a travel state of thesubject vehicle; a second step of acquiring a necessity level of lanechange that is predetermined in the travel scene; and a third step ofperforming correction to reduce the first range or increase the secondrange when the necessity level is a first determination value or more ascompared with when the necessity level is less the first determinationvalue.
 2. The travel control method according to claim 1, wherein thethird step includes performing correction to increase the first range orreduce the second range when the necessity level is less than a seconddetermination value as compared with when the necessity level is thesecond determination value or more, wherein the second determinationvalue is smaller than the first determination value.
 3. The travelcontrol method according to claim 1, wherein the travel scene includesat least one of a scene of heading to a destination, a scene in whichthe first lane is obstructed ahead, a scene in which an emergencyvehicle is approaching, a scene in which a parking vehicle exists aheadin the first lane, and a scene of overtaking a preceding vehicletraveling ahead in the first lane, and the necessity level is set foreach travel scene.
 4. The travel control method according to claim 1comprising: estimating the second range after a predetermined time; andpermitting the subject vehicle to change lanes when the second rangeafter the predetermined time includes the first range.
 5. A travelcontrol apparatus comprising: a first detector configured to detect anobstacle around a subject vehicle traveling in a first lane; a seconddetector configured to detect a second lane adjacent to the first lane;and a controller configured to: set a first range at a target positionfor lane change in the second lane, the first range having a size equalto or larger than a size which the subject vehicle occupies on a roadsurface; detect a range in the second lane as a second range, the rangein the second lane being located at a side of the subject vehicle, theobstacle being absent in the range in the second lane; and permit thesubject vehicle to change lanes when the second range includes the firstrange, the controller being further configured to: determine a travelscene of the subject vehicle on a basis of a travel state of the subjectvehicle; acquire a necessity level of lane change that is predeterminedin the travel scene; and perform correction to reduce the first range orincrease the second range when the necessity level is a predeterminedvalue or more as compared with when the necessity level is less thepredetermined value.